Geometry issues in imported FBX file?
These black spots indeed are caused by incorrect topology, as well as inorrectly oriented normals and unsplitted faces.


Regarding house contour, which is called MASSA.



In original file faces from the house itself and from the windows are overlapping and closing each other. In the final version of the file the selected faces as well as ones closing other windows are deleted.



These are faces overlapping with themselves, at the same time they close windows. It may be better to recreate them; one way can be subdiving top edges of the house contour, and filling new faces based on new vertices.
Regarding the roof which is called DAK_ZWART. I think the face selected on the picture shouldn't be there as the window continues under it.


Tiles on the roof have overlapping geometry seen through them; it's caused by the bottom big face. Just delete it:


With above mentioned, either split normals of all the objects (I used Autosmooth option in Object Data tab, it can be Edge Split modifier as well, if you plan to export the mesh use modifier only) or set the shading to Flat to make house and other man-made objects look more flat and not too round. See How to smooth shade an object while retaining hard edges? for details.
The normals were recalculated (see  Why are some faces in my mesh darker?) and some double vertices removed for all the objects as well.